Wednesday, July 30, 2008

From an article copied at bottom, in National Geographic online (passed on to me by a friend):

"In 2005 data from NASA's Mars Global Surveyor and Odyssey missions revealedthat the carbon dioxide "ice caps" near Mars's south pole had been diminishingfor three summers in a row. Habibullo Abdussamatov, head of space research atSt. Petersburg's Pulkovo Astronomical Observatory in Russia, says the Mars datais evidence that the current global warming on Earth is being caused by changesin the sun. "The long-term increase in solar irradiance is heating both Earthand Mars," he said. Abdussamatov believes that changes in the sun's heat outputcan account for almost all the climate changes we see on both planets. "

Some of you may have seen this. Interesting that it is on a National Geographic website.

"The conventional theory is that climate changes on Mars can be explainedprimarily by small alterations in the planet's orbit and tilt, not by changes inthe sun. Mars and Earth wobble in different ways, and most scientists think itis pure coincidence that both planets are between ice ages right now. "

This is just one example of how desperately the National Geographic is trying to spin this story to make the theory look bad. The story is replete with context-dropping, arguments from authority, and links to other Geographic stories that support global warming.

"Perhaps the biggest stumbling block in Abdussamatov's theory is his dismissalof the greenhouse effect, in which atmospheric gases such as carbon dioxide helpkeep heat trapped near the planet's surface."

Well, no, I don't think it does. What keeps the Earth warm is 100 miles thick of atmosphere that has been heated up by the sun. Any gas is not a bad insulator, which is why we all have double pane glass. The warm air near the surface of the Earth has a heat capacity, just like a hot iron. It takes awhile for the heat to be radiated through the insulating layers of air between the Earth and space. And every layer stores some heat as well.

These are all noble gases. Is CO2 a noble gas? No. It will have *worse* insulation qualities. Makes one suspicious of whether it “heat traps”.

So what would be the "R" rating of a double-pane window filled with the "heat-trapping" of CO2? Probably not so good. (You could do an experiment pretty easy... get a window filled with CO2, then compare the rate of heat loss to a conventional window.

Without trying to do pure science and claim I’m proving anything, let me do a brief investigation based on my hypothesis, to cast doubt on the CO2 “heat trapping” premise.

Let me start from my idea (I shouldn’t formalize it as a “hypothesis”) that the principal reason the Earth stays warm is that the total mass of the atmosphere has a heat capacity, and the gas of the atmosphere simultaneously acts like an insulator, retarding the rate of heat loss into outer space. That is, during the day, sunlight heats the atmosphere (and the ground under it), and during the night it cools by radiation into space. The heat near the Earth has to radiate up through the layers of atmosphere before escaping into the vacuum, but the atmospheric gas insulates to slow the loss of heat.

One could do a day’s worth of research to calculate this pretty exactly, by getting the values of heat capacity and thermal conductivity (higher conductivity = more rapid heat loss) for air and its constituents (O2, N2, CO2, etc) and admixtures thereof for each pressure and temperature at every altitude, and from that, do a simple numerical integration to arrive at the rate of heat loss after the sun goes down.

That is, if I wanted to prove this, I’d pretend the atmosphere is made of many thin layers of gas-filled double paned glass windows. Each layer insulates the temperature of the atmosphere below it, and passes a little bit of heat to the layer above it at a certain rate.

I could do this, and it’s not a hard calculation, but I don’t want to frighten or bore you.

So just consider this a little more qualitatively, using a little data taken from one website:

We find that the thermal conductivity of air is about 4 times lower than CO2.We also find that the heat capacity of air is a little less than that of CO2.

Now, if CO2 is really a “heat trapping gas”, causing the temperature of the Earth to rise, shouldn’t the thermal conductivity of CO2 be *lower* than Air? Instead, it’s higher. That is, more CO2 should cause more rapid heat loss, leading to the *opposite* effect of heat trapping...

Even under the most dire global warming scenario, the concentration of CO2 in the atmosphere isn’t more than a percent or so of the total atmosphere, so the extra heat capacity of CO2 will have an inconsequential effect. All the effect is in the insulating properties, which are based on the thermal conductivity. Ergo, CO2 is probably not a heat trapping gas.Now, you could argue that increased CO2 in the upper atmosphere might increase the transmissivity of solar radiation from lower and higher spectral wavelengths, thereby increasing the heating of the atmosphere during the day, thereby causing global warming.

But that’s not “heat trapping”. That’s “energy absorption”, or whatever you want to call it. Once the energy gets *into* the atmosphere and is stored there in the thermal motion of gas molecules, the heat-trapping effect is supposed to be what’s causing the global temperature rise. And if the data is reasonably representative of actual atmospheric pressure, temperature (it’s based on data from about 80C to -150C at near-atmospheric pressures) I don’t see how to reconcile the higher thermal conductivity of CO2 with heat trapping hypothesis. Ipse dixit. Et cum spiri, two two-oh. De gustibus non est disputandum. Non est ad astra mollis e terris via. Whatever.

Simultaneous warming on Earth and Mars suggests that our planet's recent climate changes have a natural -- and not a human-induced -- cause, according to one scientist's controversial theory.

Earth is currently experiencing rapid warming, which the vast majority of climate scientists says is due to humans pumping huge amounts of greenhouse gases into the atmosphere. (Get an overview: "Global Warming Fast Facts".)Mars, too, appears to be enjoying more mild and balmy temperatures.In 2005 data from NASA's Mars Global Surveyor and Odyssey missions revealed that the carbon dioxide "ice caps" near Mars's south pole had been diminishing for three summers in a row.

Habibullo Abdussamatov, head of space research at St. Petersburg's Pulkovo Astronomical Observatory in Russia, says the Mars data is evidence that the current global warming on Earth is being caused by changes in the sun.

"The long-term increase in solar irradiance is heating both Earth and Mars," he said.

Solar CyclesAbdussamatov believes that changes in the sun's heat output can account for almost all the climate changes we see on both planets.

Mars and Earth, for instance, have experienced periodic ice ages throughout their histories.

"Man-made greenhouse warming has made a small contribution to the warming seen on Earth in recent years, but it cannot compete with the increase in solar irradiance," Abdussamatov said.

By studying fluctuations in the warmth of the sun, Abdussamatov believes he can see a pattern that fits with the ups and downs in climate we see on Earth and Mars.

Abdussamatov's work, however, has not been well received by other climate scientists.

All planets experience a few wobbles as they make their journey around the sun. Earth's wobbles are known as Milankovitch cycles and occur on time scales of between 20,000 and 100,000 years.

These fluctuations change the tilt of Earth's axis and its distance from the sun and are thought to be responsible for the waxing and waning of ice ages on Earth.

Mars and Earth wobble in different ways, and most scientists think it is pure coincidence that both planets are between ice ages right now.

"Mars has no [large] moon, which makes its wobbles much larger, and hence the swings in climate are greater too," Wilson said.

No GreenhousePerhaps the biggest stumbling block in Abdussamatov's theory is his dismissal of the greenhouse effect, in which atmospheric gases such as carbon dioxide help keep heat trapped near the planet's surface.He claims that carbon dioxide has only a small influence on Earth's climate and virtually no influence on Mars.

But "without the greenhouse effect there would be very little, if any, life on Earth, since our planet would pretty much be a big ball of ice," said Evan, of the University of Wisconsin.

Most scientists now fear that the massive amount of carbon dioxide humans are pumping into the air will lead to a catastrophic rise in Earth's temperatures, dramatically raising sea levels as glaciers melt and leading to extreme weather worldwide.

Abdussamatov remains contrarian, however, suggesting that the sun holds something quite different in store.

"The solar irradiance began to drop in the 1990s, and a minimum will be reached by approximately 2040," Abdussamatov said. "It will cause a steep cooling of the climate on Earth in 15 to 20 years."

I had a discussion with someone about why Venus is so much hotter than Earth. Is it because Venus is 96.5% CO2, which is acting as a "heat trap"? Or can the higher temperature be explained by other causes?

I made the point that, being closer to the Sun, the radiant energy received by Venus is about 88% higher than Earth (67 million miles away vs. 92 million, average, and intensity increases as the square of distance). The Earth has an average temperature of 287K, while Venus has an average temperature of 855K. Therefore, 1.88 * 287K = 541K is the least that the temperature of Venus should be, simply because it's closer to the sun.

But the discrepancy makes one wonder -- if Venus is still subject to heat trapping, how else does the temperature get up to 855K?

I made a hand-waving argument that the higher surface pressure on Venus (80 atmospheres) should have an effect because of the higher heat capacity of the denser atmospheric gas. I argued from the chemistry formula PV = nRT, and, while it points in the right direction, doesn't give a correct answer within an order of magnitude.

So I considered whether the higher molecular density of CO2 on Venus is a factor. I checked this: Carbon has an atomic weight of 12, Nitrogen 14, Oxygen 16. Average molecular weight of CO2 is 12+32 = 44. But the weighted average for Venus's atmosphere is 43.44 (96.5% CO2, 3.5% N2). Earth's atmosphere is 78.1% N2, 20.9% O2 and 0.9% Ar. Monoatomic argon has an atomic weight of 36. Average molecular weight of Earth's atmosphere is 28.91.

Multiplying my original estimate of the Venusian temperature times a density correction factor, I get 541K * (43.44 / 28.91) = 813K as the estimated surface temperature of Venus. This is pretty close to the actual surface temperature of Venus, 855K. It still leaves a little room for heat trapping effects, though. T'would be interesting to re-do the calculation based on the isotopic distributions (different number of neutrons) in the N2, O2, etc (they will have a big effect), or the amount of monoatomic vs diatomic species (ie, O vs O2, N vs N2) to see if the answer gets better or worse.

I wouldn't publish this reasoning in a scientific journal without more work, but it's worth pondering. Simple formula that gives reasonably correct results sometimes have valid foundations when analyzed more deeply. Better than a lot of the crap you'll read in professional journals, anyway.

Postscript (12/6/09): Venusians Discredit RobbI re-did this calculation, and now my numbers aren't quite adding up. The situation is more complex than I assumed. My biggest error is that temperature increases only as the fourth root of solar power (per Stefan's Law of Radiancy), but I also got a wrong value of the average Venusian temperature, which should be 737K (I accidentally converted "F" to "K"), but I'm still unsure -- some reports give close to 900K as an equatorial surface temperature, and the "average" numbers I find on the web are all over the map, from 673K to 755K.

I did, however, find that the ratio of heat capacity to thermal conductivity of a gas is relatively independent of pressure and temperature, so that supports using my molar mass hypothesis without corrections for P and T, but the calculated surface temperature is still coming out too low (508K). This points to at least a higher thermal resistance of the Venusian atmosphere, as compared to Earth. This makes sense from several aspects -- the high concentration of CO2, and the fact that the atmosphere of Venus is 94 times heavier than Earth. Heat capacity is roughly proportional to mass, but as I said, so is thermal resistance. A small difference of two big numbers can make a big difference.

I tried to find high temperature CO2 thermal conductivity data to incorporate this, but couldn't. However, the higher thermal resistance is supported by a Venusian blackbody temperature of 231K (per Nasa) as compared to Earth's 254K. Even correcting thermal resistance based on the ratio of blackbody temperatures (and solar fluence closer to the sun) I still only get up to 644K for the average Venusian surface temperature.

Another aspect -- the much more massive Venusian atmosphere is almost twice as high as Earth's -- this would increase the thermal resistance, and temper the blackbody radiation. Trap more heat.

Another aspect -- the only atmospheric composition data I could find apparently only applies to the surface. No information on what it is at 15.9km or higher.

Another factor I learned is that much of the excess heat could be coming from the core of Venus (the surface was reportedly molten only 500 million years ago), and with the high atmospheric thermal resistance, that would raise surface temperatures significantly. So, in conclusion, I have too little data to really make a good calculation. The devil's in the details. Sigh.

Thursday, July 10, 2008

Two articles here by Bill Gertz, military reporter of the Washington Times. In one, the disheartening news that Special Operations is being subordinated in importance because the CIA and State Department and wusses in DOD don't want to kill Al Qaeda in Pakistan.

Said one Pentagon official: "The reason some Pentagon leaders appear to be so indecisive about President Bush's order to catch Osama bin Laden dead or alive is that they have not unleashed the dogs of war. Too many bureaucrats have blocked ideas from the aggressive U.S. commandos in Afghanistan and at SOCOM headquarters who just want to carry out the president's orders to stop al Qaeda from rebuilding."

In the second article, the interesting point that the Chinese ARE willing to unleash the dogs of war. They are developing a strategic long-range missile with the single purpose of destroying our aircraft carriers, and it is anticipated that they will sell this to any country that wants it -- Iran, Venezuela, Cuba, etc, etc.

Defense officials are criticizing what they say is the failure to capture or kill top al Qaeda leaders because of timidity on the part of policy officials in the Pentagon, diplomats at the State Department and risk-averse bureaucrats within the intelligence community.

Military special operations forces (SOF) commandos are frustrated by the lack of aggressiveness on the part of several policy and intelligence leaders in pursuing al Qaeda leader Osama bin Laden and his top henchmen, who are thought to have hidden inside the tribal areas of Pakistan for the past 6½ years.

The focus of the commandos' ire, the officials say, is the failure to set up bases inside Pakistan's tribal region, where al Qaeda has regrouped in recent months, setting up training camps where among those being trained are Western-looking terrorists who can pass more easily through security systems. The lawless border region inside Pakistan along the Afghan border remains off-limits to U.S. troops.The officials say that was not always the case. For a short time, U.S. special operations forces went into the area in 2002 and 2003, when secret Army Delta Force and Navy SEALs worked with Pakistani security forces.

That effort was halted under Deputy Secretary of State Richard L. Armitage, who recently blamed Pakistan for opposing the joint operations. Mr. Armitage, however, also disclosed his diplomatic opposition to the commando operations. Mr. Armitage, an adviser to Republican presidential contender Sen. John McCain, told the New York Times last month that the United States feared pressuring Pakistani leaders for commando access and that the Delta Force and SEALs in the tribal region were "pushing them almost to the breaking point.

"However, the officials said that without the training and expertise of the U.S. commandos, Pakistani forces took heavy casualties in the region, with about 1,000 troops killed by terrorists and their supporters.A Dong Feng missile is on display at the Military Museum of the Chinese People's Revolution. China's anti-carrier ballistic missile effort, including an upcoming test firing, is closely watched by the U.S.

Another major setback for aggressive special operations activities occurred recently with a decision to downgrade the U.S. Special Operations Command. Under Defense Secretary Donald H. Rumsfeld, the command in 2004 began to shift its focus from support and training to becoming a front-line command in the covert war to capture and kill terrorists. In May, SOCOM, as the command is called, reverted to its previous coordination and training role, a change that also frustrated many SOF commandos.

Critics in the Pentagon of the failure to more aggressively use the 50,000-strong SOF force say it also is the result of a bias by intelligence officials against special forces, including Pentagon policy-makers such as former CIA officer Michael Vickers, currently assistant defense secretary for special operations; former CIA officer Mary Beth Long, assistant defense secretary for international security affairs; and Defense Secretary Robert M. Gates, a former CIA director.

The officials said the bias among intelligence officials against aggressive military special operations is long-standing. As evidence, they note that one of the very few recommendations of the 9/11 commission ignored by President Bush was the panel's call for giving the Pentagon the lead role in paramilitary operations.

The commission report stated that "lead responsibility for directing and executing paramilitary operations, whether clandestine or covert, should shift to the Defense Department." That has not occurred, and the officials said one result is that bin Laden and his deputies remain at large.

Said one Pentagon official: "The reason some Pentagon leaders appear to be so indecisive about President Bush's order to catch Osama bin Laden dead or alive is that they have not unleashed the dogs of war. Too many bureaucrats have blocked ideas from the aggressive U.S. commandos in Afghanistan and at SOCOM headquarters who just want to carry out the president's orders to stop al Qaeda from rebuilding.

"Pentagon press secretary Geoff Morrell declined to address any specifics of special operations policies but said he thinks senior commanders do not share the critics' views.On the hunt for bin Laden, Mr. Morrell said: "No one should question our commitment to bringing Osama bin Laden and the rest of his cowardly lieutenants to justice, one way or another. It will happen. it's just a question of when."

China targets carriers

China is close to deploying a new conventionally armed strategic missile capable of hitting U.S. aircraft carriers and other warships at sea.A defense intelligence official said a test of the new weapon is expected, but the timing is not known. A second official also said the Chinese anti-carrier ballistic missile effort, including an anticipated test firing, is being watched closely.

Defense officials said the new missile — a precision guided CSS-5 medium-range missile — is as great or greater a concern for some military planners as China's new anti-satellite weapon, which was first tested successfully against an orbiting Chinese weather satellite in January 2007.

The reason: The backbone of U.S. plans to defend Taiwan from Chinese attack calls for rushing more than half the U.S. aircraft carrier strike groups to the island in the event Beijing follows through on threats to use force to reunite the island with the mainland. Carrier-killing missiles are viewed as one of the most important strategic weapons in the Beijing arsenal because they will be able to block the rapid deployment of U.S. forces to the region considered vital to any Taiwan defense or defense of other allies in the region.

Richard Fisher, a specialist on the Chinese military with the International Assessment and Strategy Center, said the upcoming test of a medium-range anti-ship ballistic missile (ASBM) would not be China's first. "It would appear that the [People's Liberation Army] may now be developing three types of ASBMs," he said.Two of the missiles are based on the CSS-5, also known as the DF-21, and Chinese Internet photos reveal what looks like a maneuvering warhead on the missile similar in design to warheads deployed on the U.S. Pershing-2 medium-range missile. The Pershing-2, dismantled in the 1980s, used a radar-digital map guidance system, and Mr. Fisher thinks the new Chinese anti-ship missile could use a combination of active radar and optical or infrared guidance.

A third anti-ship ballistic missile is expected to be a longer-range variant of the CSS-5 first seen in 2006 that may have multiple warheads.

"It is bad enough that these missiles are being developed and can soon target U.S. naval forces from China," Mr. Fisher said. "But we should also expect that China will eventually place these missiles on ships and submarines and sell them to its rogue allies."

"The Ahmadinejads, Castros and Chavezes of the world would love to have these missiles to hold the U.S. Navy at bay," he said, noting that the U.S. needs a similar capability to target China's growing navy.

U.S. Navy missile defense interceptors also should be upgraded to counter the new Chinese carrier killers, he said.

Bill Gertz covers national security affairs. He can be reached at 202/636-3274, or at insidethering@washingtontimes.com.

Monday, July 7, 2008

The title of this post is, of course, my corruption of the title for an excellent article Ayn Rand wrote many years ago, "Censorship, Local and Express" (reprinted in Philosophy: Who Needs It). The article below is interesting if you are concerned about the First Amendment, censorship, and are willing to wade through the whole damn thing. Without excerpting extensively like I usually do, the upshot is that web-hosting companies are deleting customer content, often without their knowledge, and for sure without their approval.

Of course, private companies have the right to delete content (which the article acknowledges), but the subtext never discussed here is that these companies aren't deleting "objectionable content" out of any desire to defend their own values (whatever corporate values are in today's world), but simply to avoid litigation by private parties and government agencies, who *illegitimately* threaten the First Amendment rights of the companies themselves to host web content. For instance, in one case below,

Unable to stop purveyors of child pornography directly, New York AttorneyGeneral Andrew Cuomo recently persuaded three major access providers to disableonline newsgroups that distribute such images. But rather than cut off thosespecific newsgroups, all three decided to reduce administrative hassles by alsodisabling thousands of legitimate groups devoted to TV shows, the New York Metsand other topics.

The companies are only protecting their interests and minimizing expenses -- as they have a right to. And of course, in the case of child porn, there is a legitimate government interest -- a web hosting service can be charged with facilitating a crime if they know this stuff is passing through their equipment. But it goes far beyond this. For instance, provider

Network Solutions LLC decided to suspend a Web hosting account that Dutchfilmmaker Geert Wilders was using to promote a movie that criticizes the Quran —before the movie was even posted and without the company finding any actualviolation of its rules.

which is contemptible. In other words, *legitimate* criticism may be removed, if some lower-level peon feels, according to *his* values (not the company's), that he objects to something. Again, of course it's a private company, and he's acting as their representative, but the oversight is poor (if you read the article, and just think about it logically).

The cash value of this article is essentially that it highlights a situation where non-objective laws have emerged, which have given private parties and government agencies the power of defacto censorship -- still somewhat limited, but growing. Whether or not you can move your website or blog somewhere else is irrelevant -- they can intimidate internet web providers into removing content *whether or not it is illegal, or defamatory, or objectionable to the values of those running the company*. The censorship in this context is not primarily of the customers who use the company, but of the company itself.

The danger here is that corporations, out of simple self-preservation, will almost always choose the path of least resistance, and will only rarely spend money in court (millions, for sure) to defend their rights. This is leading today to a situation where the web, once touted as the great liberator of free speech, is becoming the agent of widespread defacto censorship. For instance, note that the web is rapidly coming to dominate as the main source of *news*. It is not a large jump from restricting what bloggers say to what news is reported. It isn't a large jump to restricting what your *email* says.

Whether or not you can move to a different hosting service, the trend is towards *all* corporations to do the same. Whether or not you can host your own website, the trend is toward the law coming after *you*.

NEW YORK - Rant all you want in a public park. A police officer generally won't eject you for your remarks alone, however unpopular or provocative.

Say it on the Internet, and you'll find that free speech and other constitutional rights are anything but guaranteed.

Companies in charge of seemingly public spaces online wipe out content that's controversial but otherwise legal. Service providers write their own rules for users worldwide and set foreign policy when they cooperate with regimes like China. They serve as prosecutor, judge and jury in handling disputes behind closed doors.

The governmental role that companies play online is taking on greater importance as their services — from online hangouts to virtual repositories of photos and video — become more central to public discourse around the world. It's a fallout of the Internet's market-driven growth, but possible remedies, including government regulation, can be worse than the symptoms.

Dutch photographer Maarten Dors met the limits of free speech at Yahoo Inc.'s photo-sharing service, Flickr, when he posted an image of an early-adolescent boy with disheveled hair and a ragged T-shirt, staring blankly with a lit cigarette in his mouth.

Without prior notice, Yahoo deleted the photo on grounds it violated an unwritten ban on depicting children smoking. Dors eventually convinced a Yahoo manager that — far from promoting smoking — the photo had value as a statement on poverty and street life in Romania. Yet another employee deleted it again a few months later.

"I never thought of it as a photo of a smoking kid," Dors said. "It was just of a kid in Romania and how his life is. You can never make a serious documentary if you always have to think about what Flickr will delete."

There may be legitimate reasons to take action, such as to stop spam, security threats, copyright infringement and child pornography, but many cases aren't clear-cut, and balancing competing needs can get thorny.

"We often get caught in the middle between a rock and a hard place," said Christine Jones, general counsel with service provider GoDaddy.com Inc. "We're obviously sensitive to the freedoms we have, particularly in this country, to speak our mind, (yet) we want to be good corporate citizens and make the Internet a better and safer place."

In Dors' case, the law is fully with Yahoo. Its terms of service, similar to those of other service providers, gives Yahoo "sole discretion to pre-screen, refuse or remove any content." Service providers aren't required to police content, but they aren't prohibited from doing so.

While mindful of free speech and other rights, Yahoo and other companies say they must craft and enforce guidelines that go beyond legal requirements to protect their brands and foster safe, enjoyable communities — ones where minors may be roaming.

Guidelines help "engender a positive community experience," one to which users will want to return, said Anne Toth, Yahoo's vice president for policy.

Dors ultimately got his photo restored a second time, and Yahoo has apologized, acknowledging its community managers went too far.

Heather Champ, community director for Flickr, said the company crafts policies based on feedback from users and trains employees to weigh disputes fairly and consistently, though mistakes can happen.

"We're humans," she said. "We're pretty transparent when we make mistakes. We have a record of being good about stepping up and fessing up."

But that underscores another consequence of having online commons controlled by private corporations. Rules aren't always clear, enforcement is inconsistent, and users can find content removed or accounts terminated without a hearing.

Appeals are solely at the service provider's discretion.Users get caught in the crossfire as hundreds of individual service representatives apply their own interpretations of corporate policies, sometimes imposing personal agendas or misreading guidelines.

To wit: Verizon Wireless barred an abortion-rights group from obtaining a "short code" for conducting text-messaging campaigns, while LiveJournal suspended legitimate blogs on fiction and crime victims in a crackdown on pedophilia. Two lines criticizing President Bush disappeared from AT&T Inc.'s webcast of a Pearl Jam concert.

All three decisions were reversed only after senior executives intervened amid complaints.Inconsistencies and mysteries behind decisions lead to perceptions that content is being stricken merely for being unpopular.

"As we move more of our communications into social networks, how are we limiting ourselves if we can't see alternative points of view, if we can't see the things that offend us?" asked Fred Stutzman, a University of North Carolina researcher who tracks online communities.

First Amendment protections generally do not extend to private property in the physical world, allowing a shopping mall to legally kick out a customer wearing a T-shirt with a picture of a smoking child.

With online services becoming greater conduits than shopping malls for public communications, however, some advocacy groups believe the federal government needs to guarantee open access to speech. That, of course, could also invite meddling by the government, the way broadcasters now face indecency and other restrictions that are criticized as vague.

Others believe companies shouldn't police content at all, and if they do, they should at least make clearer the rules and the mechanisms for appeal.

"Vagueness does not inspire the confidence of people and leaves room for gaming the system by outside groups," said Lauren Weinstein, a veteran computer scientist and Internet activist. "When the rules are clear and the grievance procedures are clear, then people know what they are working with and they at least have a starting point in urging changes in those rules."

But Marjorie Heins, director of the Free Expression Policy Project, questions whether the private sector is equipped to handle such matters at all. She said written rules mean little when service representatives applying them "tend to be tone-deaf. They don't see context."

At least when a court order or other governmental action is involved, "there's more of a guarantee of due process protections," said Robin Gross, executive director of the civil-liberties group IP Justice. With a private company, users' rights are limited to the service provider's contractual terms of services.

Jonathan Zittrain, a Harvard professor who recently published a book on threats to the Internet's openness, said parties unhappy with sensitive materials online are increasingly aware they can simply pressure service providers and other intermediaries."

Going after individuals can be difficult. They can be hard to find. They can be hard to sue," Zittrain said. "Intermediaries still have a calculus where if a particular Web site is causing a lot of trouble ... it may not be worth it to them."

Unable to stop purveyors of child pornography directly, New York Attorney General Andrew Cuomo recently persuaded three major access providers to disable online newsgroups that distribute such images. But rather than cut off those specific newsgroups, all three decided to reduce administrative hassles by also disabling thousands of legitimate groups devoted to TV shows, the New York Mets and other topics.

Gordon Lyon, who runs a site that archives e-mail postings on security, found his domain name suddenly deactivated because one entry contained MySpace passwords obtained by hackers.

He said MySpace went directly to domain provider GoDaddy, which effectively shut down his entire site, rather than contact him to remove the one posting or replace passwords with asterisks. GoDaddy justified such drastic measures, saying that waiting to reach Lyon would have unnecessarily exposed MySpace passwords, including those to profiles of children.

Meanwhile, in response to complaints it would not specify, Network Solutions LLC decided to suspend a Web hosting account that Dutch filmmaker Geert Wilders was using to promote a movie that criticizes the Quran — before the movie was even posted and without the company finding any actual violation of its rules.

Service providers say unhappy customers can always go elsewhere, but choice is often limited.

Many leading services, particularly online hangouts like Facebook and News Corp.'s MySpace or media-sharing sites such as Flickr and Google Inc.'s YouTube, have acquired a cachet that cannot be replicated. To evict a user from an online community would be like banishing that person to the outskirts of town.

Other sites "don't have the critical mass. No one would see it," said Scott Kerr, a member of the gay punk band Kids on TV, which found its profile mysteriously deleted from MySpace last year. "People know that MySpace is the biggest site that contains music."

MySpace denies engaging in any censorship and says profiles removed are generally in response to complaints of spam and other abuses. GoDaddy also defends its commitment to speech, saying account suspensions are a last resort.

Few service providers actively review content before it gets posted and usually take action only in response to complaints.

In that sense, Flickr, YouTube and other sites consider their reviews "checks and balances" against any community mob directed at unpopular speech — YouTube has pointedly refused to delete many video clips tied to Muslim extremists, for instance, because they didn't specifically contain violence or hate speech.Still, should these sites even make such rules? And how can they ensure the guidelines are consistently enforced?

YouTube has policies against showing people "getting hurt, attacked or humiliated," banning even clips OK for TV news shows, but how is YouTube to know whether a video clip shows real violence or actors portraying it? Either way, showing the video is legal and may provoke useful discussions on brutality.

"Balancing these interests raises very tough issues," YouTube acknowledged in a statement.

Unwilling to play the role of arbiter, the group-messaging service Twitter has resisted pressure to tighten its rules.

"What counts as name-calling? What counts as making fun of someone in a way that's good-natured?" said Jason Goldman, Twitter's director of program management. "There are sites that do employ teams of people thatdo that investigation ... but we feel that's a job we wouldn't do well."

Other sites are trying to be more transparent in their decisions.Online auctioneer eBay Inc., for instance, has elaborated on its policies over the years, to the extent that sellers can drill down to where they can ship hatching eggs (U.S. addresses only) and what items related to natural disasters are permissible (they must have "substantial social, artistic or political value"). Hypothetical examples accompany each policy.

LiveJournal has recently eased restrictions on blogging. The new harassment clause, for instance, expressly lets members state negative feelings or opinions about another, and parodies of public figures are now permitted despite a ban on impersonation. Restrictions on nudity specifically exempt non-sexualized art and breast feeding.

The site took the unusual step of soliciting community feedback and setting up an advisory board with prominent Internet scholars such as Danah Boyd and Lawrence Lessig and two user representatives elected in May.

The effort comes just a year after a crackdown on pedophilia backfired. LiveJournal suspended hundreds of blogs that dealt with child abuse and sexual violence, only to find many were actually fictional works or discussions meant to protect children. The company's chief executive issued a public apology.

Community backlash can restrain service providers, but as Internet companies continue to consolidate and Internet users spend more time using vendor-controlled platforms such as mobile devices or social-networking sites, the community's power to demand free speech and other rights diminishes.

Weinstein, the veteran computer scientist, said that as people congregate at fewer places, "if you're knocked off one of those, in a lot of ways you don't exist."